This study examined the behavior of corrosion potential (Ecorr) of iron and copper exposed to drinking water during episodes of stagnation and flow that are characteristic for water distribution systems and household plumbing. These measurements established that the transient behavior of the corrosion potential of these metals has distinct features reflecting complex processes associated with metal release. In the case of iron, Ecorr values decrease prominently during stagnation while in flow conditions, the corrosion potential increases to reach a quasi-steady state. Experiments with varying concentrations of dissolved oxygen showed that for iron, the decrease of Ecorr is likely to be associated with the consumption of dissolved oxygen by the corroding metal or surface scales. Iron release measurements showed that the Ecorr values measured prior to or after stagnation episodes were correlated with the logarithms of concentrations of total   iron. The slope of this dependence showed that the observed correlations corresponded to the coupling between the oxidant consumption and changes of the redox status of iron in the corrosion scales or Fe(0) per se. In the case of copper, the extent of changes of the corrosion potential was less prominent and the behavior of the corrosion potential was in some cases non-monotonic. This was interpreted to reflect the kinetics of the consumption of oxidants and release of copper into the ambient solution. These results demonstrate that in situ Ecorr measurements can be a sensitive method with which to ascertain effects of hydrodynamic conditions and short-term variations of water chemistry on metal release and corrosion in drinking water. This approach is valuable practically because Ecorr measurements are precise, can be carried out in situ and do not affect the state of exposed surface.

Transient behavior of the corrosion potential of metals exposed to drinking water: Effects of stagnation and flow conditions and their relationship with metal release

248th National Meeting (2014)

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